Field of the Invention
The present invention relates to a current output-type detection device that changes an amount of current consumption of the device itself in response to a detection result.
Background Art
For example, in a current output-type detection device that changes an amount of current consumption of the device itself in response to a detection result of a magnetic sensor or the like, it is important, while suppressing an increase of an amount of power consumption, to suppress lowering of detection accuracy even if variations occur in a power supply voltage (for example, refer to Patent Document 1).
FIG. 8 illustrates a block diagram of a conventional current output-type detection device. The conventional current output-type detection device 1 is composed of: a detection circuit unit 4 composed of a magnetic detection element and the like; and a starting function unit 5 that starts up the detection circuit unit 4. In the detection device 1, an anode side of a power supply source 2 is connected to a power supply terminal Vcc thereof, and a cathode side of the power supply source 2 is connected to a ground terminal Vss thereof through a measuring resistor R. A measurement unit 3 is connected in parallel to both ends of the measuring resistor R.
The starting function unit 5 functions as a constant current source that supplies a constant current In to the detection circuit unit 4, and the starting function unit 5 itself flows a starting current Is therefrom. The detection circuit unit 4 starts up by the constant current In supplied from the starting function unit 5, and outputs a detection current Ix that shows a detection result. Hence, a current consumption I of the detection device 1 becomes a total sum of the starting current Is and the detection current Ix. Therefore, the measurement unit 3 can recognize the detection result by measuring this current consumption I.
Here, with regard to the detection device 1, a power supply circuit unit and a current stabilization circuit unit are provided between the starting function unit 5 and the detection circuit unit 4, whereby fluctuation of the current consumption of the detection device, the fluctuation being caused by the variations of the power supply voltage, is suppressed, and the detection device 1 becomes capable of obtaining the detection result with high accuracy. Hence, current values of the starting current Is and the detection current Ix can be set low, and accordingly, the detection device 1 can reduce an amount of power consumption.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2007-156997